Grizzly and screen for grading materials



Jan. 23, l945. w.'Ross lGRIZZLY AND SCREEN FOR GRADING MATERIALS Filed Jan. 8, 1943 4 Sheets-Sheet 1 n A lnmummvd nlhnnuv ul.. .nwuyhumwnmmxkuunlnvxhn x 1 1 x l l l r 1 x l x v 1 l if..

.,U lxflnwnvzh. l .l 1 x r s x e u jam. 23, i945. W, ROSS GRIZZLY AND SCREEN FOR GRADING MATERIALS Filed Jan. 8, 1945 4 SheeGS-Shee'( 2 @A A N Jam. 23, 1945. w. Ross GRIZZLY AND SCREEN FOR GRADING MATERIALS 4 Sheets-Sheet 3 Filed Jan. 8, 1943 1i i@ Inl/enig? Wjo 55 Jan., 23, 1945. w. Ross 2,367,964

GRIZZLY AND SCREEN FOR GRADING MATERIALS Filed Jan. 8, 1943 4 Sheets-Sheet 4 Patented Jan. 23, 1945 GRIZZLY AND SCREEN FOR GRADING MATERIALS William Ross, Surbiton, England Application January 8, 1943', Serial No.. 471,727

In. Great Britain March117, 1942y 4 Claims.

`This invention relates to screens for grading materials and particularly to what are commonly known as grizzlies and screens such as are described, for example, in my prior British patent specications Nos. 123,201, 179,562 and 297,706, and which in general comprise two sets of transverse bars supported substantially horizontally and arranged to move in closed orbits of different lengths, which orbits, however, coincide in the screening zone in which the said bars will be separated by spaces of predetermined size. With the divergence of the orbits after passing the screening zone the spaces between the bars should be automatically increased in size and attain a maximum size when the bars are traversing the sections of their orbits directly beneath the screening zone whereby fines (that is, the small pieces of material) which pass between the bars in the screening zone are passed freely through the spaces betweenysaid bars when traversing the lower or return portions of their orbits.

`With such screening arrangements as hitherto adopted it has been found in general that trouble is caused by the heavy apron of bars pressinglaterally or sideways due to a number of factors connected with the load and namely (a) the way in which the load is fed to the screen; (b) the way the load disposes itself on the screen, and (c) the way the load leaves the screen. It must be understood that the grizzly is normally employed under conditions where wagon loads up to 25 tons and containing pieces up to 5' cube and weighing up to 4 tons are crash dumped on to the feed end of the screen or grizzly. It is therefore obvious that the initial pieces of material reaching the grizzly may hit the bars thereof in a manner that will produce sideways forces. Sideways forces are also produced by the load on the apron of bars being more to one side and/or the apron being pressed out of level locally or wholly and by the uneven lateral discharge of the material from the grizzly due for example to a large piece leaving earlier than its neighbour or to a bank of smaller material slufling o at one side, a trouble which is accentuated in the case of small and sticky material which may arrive at the discharge end in.

a bank 3 or 4' thick. At one moment the. end of this bed mayr be steep-sometimes vertical,

sometimes even overhanging-and the; next moby which the grizzly bars are carried', andthe. sprockets, over which the chains at' each` side ofA the grizzly bars pass, and, especially when the; apron is forced to one side at one place and held or forced to the other side in another place, the. chain links. break and/or the bar ends are bent or broken.

The object of my invention is to provide an improved construction Which will be. free from the, defects and disadvantages above noted, andwhich will moreover enable a sidewaysV feeding of the material on to the. grizzly barsl to be a practical. possibility.V

The invention consists in a grizzly or screen. of the kind comprising sets of main and secondiary or drop travelling screening bars arranged in pairs and extending transversely to their ydirec-- tion of travel wherein meansis provided adapted to restrict sidewaysr or lateral. movement of the bars under operating conditions due to thev action of the material loaded or supported thereon.

The invention also consists in a grizzly or screen of the kind described in my earlier patent specificationsl above referred to, wherein the screening bars bear, in the screening zone, upon a track with which the bars engage through the medium of recessed portions thereof such that sideways or lateral local movement of ther apron constituted by the bars in the screening zone is. restricted.

Also in accordance with the invention the links of chains connecting the screening bars together and serving to carry the bars through the screen'- ing zone are formed to have a certain amount of clearance where they are connected with each other such that a limited amount ofv lateral bending or distortion of the chain atY such points is permitted to take care of sideways or lateral thrusts imposed upon the screening bars by the material received thereon.

The invention also consists in screeningapparatus of. the. character described having furtherI features hereinafter referred to.

In thev accompanying drawings- Figure 1 is a side elevational view of a grizzly or screen in4 accordance with the invention,

Figure 2 is a half plan view of Figure 1,

Figure' is an end view of Figure 1,l

Figure 4 is an enlarged part sectional and fragmentary plan view of the grizzly or screen bars,

Figure 5 is a section on the line. A-A of Figure 4,

Figure 6 is. a section on the line C--C of Figthe above set up unusual side wear on the chains. ure 4.

In carrying my invention into effect in one convenient manner a grizzly or screen is provided which, like the constructions according to my earlier specifications, comprises alternate main bars I and secondary or drop bars 2 extending transversely between a pair of side and endless chains 3 to which the main bars I are pivotally connected at their ends and in order to afford a certain amount of lateral flexibility I provide the chain links 4, connected to the main bars, with their outer ends 5 somewhat narrower than their inner ends, effected for example by tapering their outer ends inwards (as shown in Figure 4), whereby a clearance D exists between the outer ends of the main links 4 and the side links 6 connected between the main links which is suflcient to permit a lateral local bending of the chains up to a certain extent without straining.

or breaking, there being enough clearance 'I between the hubs 6a of the side links and the spigoted pivot ends la of the main bars to permit such lateral movement to take place and a further clearance v8 being provided for between the holes in the main links 4 and the bearing surfaces therefor afforded by the exterior `surfaces of the corresponding hubs 6a to assist in this direction. The drop bars 2 have spigoted pivot ends 2a engageable within bushes 2b on lever arms 2c, in turn pivoted through bushes 2d at their opposite ends about the inner ends of the corresponding hubs 6a mounted upon the spigoted ends of the main` bars and, as shown in Figures 4 and 5, a certain amount .of clearance E is also provided between the various bearing surfaces thus provided.

Disposed to extend longitudinally along the inside of each chain and situated, as shown in Figures 13, near the upper run of the assembly of main and drop bars there is a plate or track 9 upon the upper edge of which the corresponding end portions of the grizzly bars bear while they move through the screening zone but whereas the drop bars 2 rest freely upon the track plate or are only slightly recessed, as indicated at I0 in Figure 4, to engage therewith the main bars I are deliberately recessed, as indicated at II, at the portions thereof which come opposite the upper edges of the track plates so that sideways or lateral 'movement of the apron, constituted by the assembly of main and drop bars, is restricted due to the engagement of the track plates within the recesses of the main grizzly bars. However, such recessing of the main grizzly bars is preferably not such as will preclude some lateral movement of the apron. Thus when the recesses in the main bars are in the form of annular recesses of channel form there is preferably some clearance provided between the sides I2 of the recesses and the side walls I3 of the portions 'of the tracks which engage therein. Preferably,

the links in such manner that the heads are pre' vented froml rotating, the heads constituting the abutments proper on the links, and they cooper` ate in turn with lateral lugs 511 on the lever arms 2c, the arrangement being shown in Figure 4.

The track plates may, as shown in Figure 3, be supported in position through the medium of springs I4 which permit a limited amount of vertical movement of the plates to take place to afford a kind of cushioning effect when the material is loaded upon the screening bars.

To provide for an even loading of the grizzly with the material to be screened, I may provide, in one of its simplest forms, a barrier I6 above the grizzly which serves to impose a limit to the maximum depth of the bed of material at any point across the width of the grizzly and causes attempted excesses of material at one point of the width of the grizzly to go to other unoccupied parts of the width thereof. Such barrier (which may consist of a plate supported above the grizzly to extend transversely across the grizzly bars near the feed end of the grizzly and, of course, be vertically spaced from the grizzly bars) may be adjusted to be higher at one side than the other to co-rrect permanent faults in or tendencies of feed.

I claim:

. 1. A grizzly or screen of the kind comprising endless chains, sets of main and secondary transverse bars arranged in pairs with the main bars of each set supported at their outer ends uponv the endless chains to lie substantially horizon-- tally and arranged to move in closed orbits of different lengths, which orbits, however, coincide in the upper run which constitutes the screening zone, a track arranged beneath the upper run of the assembled bars and all of the bars being recessed near their ends to engage with the track to restrict sideways or lateral movement of the bars.

2. A grizzly or screen according to claim 1' wherein the bars rest freely on the track in they screening zone through the medium of the re' cessed portions of the bars, which recessed portions are of attened V-shape in cross section, and in the case of the main bars have their bevelled side walls extended beyond each side of the corresponding track whereby sideways or lateral movement of the main bars in the screening zone is definitely restricted.

3. A grizzly or screen of the character described comprising spaced horizontal shafts, spaced sprockets thereon, endless chains operating about the sprockets, sets of main and Secondary transverse bars arranged in pairs with the main bars of each pair operatively connected with the chains while the secondary bars are operably connected to the main bars so as to have a swinging movement, tracks arranged longitudinally beneath the upper lays of the chains for maintaining the bars in a horizontally supported position, the main and secondary bars being grooved near their ends to engage the tracks to restrict side-Wise or lateral movement of the bars as the bars pass through the upper lay which constitutes the screening zone, and means for yieldingly supporting the tracks.

4. A grizzly or screen of the character described comprising spaced horizontal shafts, spaced sprockets thereon, endless chainsoperating about the sprockets, and including main and side links to which the main links 'are connected," main and secondary transverse bars arranged in pairs and having their respective ends trunn'ioned with the trunnions'on the main bars elongated and journaled in the side links, leverarms operatively connected to the side links and about the main and secondary 'bars being also recessed near their ends to engage the tracks to restrict sidewise or lateral movement of the bars as the -bars pass through the upper lay, and means for yield- 5 ingly supporting the tracks.

WILLIAM ROSS. 

